The Hard X-ray Modulation Telescope (HXMT) , named "Insight", is China’s first X-ray astronomy satellite. There are three main payloads onboard Insight-HXMT, the high energy X-ray telescope (20-250 keV, 5100 cm2), the medium energy X-ray telescope (5-30 keV, 952 cm2), and the low energy X-ray telescope (1-15 keV, 384 cm2). The main scientific objectives of Insight-HXMT are: (1) to scan the Galactic Plane to find new transient sources and to monitor the known variable sources, (2) to observe X-ray binaries to study the dynamics and emission mechanism in strong gravitational or magnetic fields, and (3) to find and study gamma-ray bursts with its anti-coincidence CsI detectors.